Cone Slant Height Calculator

About this calculator

The slant height of a right circular cone is found with the Pythagorean relationship l = √(r² + h²), where r is the base radius and h is the perpendicular height from the base to the apex — the slant height itself is the straight-line distance along the cone's surface from the edge of the base up to the tip.

It's the figure you actually need for real-world jobs like calculating the lateral surface area of a cone (πrl) or cutting a paper or sheet-metal template that wraps into a cone shape — traffic cones, funnels, lampshades and party hats are all built from a flat sector whose radius equals the slant height, so getting it right determines whether the pattern actually closes into a cone.